Upconverter_NoiseSource - ha7ilm/opendous GitHub Wiki

UPDATE IN PROGRESS

https://raw.githubusercontent.com/ha7ilm/opendous/master/Current_Designs/Upconverter/Upconverter_Noise_Source_Picture.jpg

The Noise Source is a basic Avalanche noise circuit. A 5V to 12V boost regulator is used to power a Zener diode which use Avalanche breakdown above 6V. The output is DC-blocked and amplified by about 40dB using two amplifiers.

https://raw.githubusercontent.com/ha7ilm/opendous/master/Current_Designs/Upconverter/Upconverter_Noise_Source_Schematic-Small.jpg

Populating Parts

The Noise Source is not fully populated on production boards. To use it you will need to purchase and populate two SOT-89 amplifier ICs (such as MMG3H21NT1), the Boost Regulator (SC4503TSKTRT), an SMA Connector (such as CONSMA003.062), a 2-pin 0.1" header (such as 961102-6404-AR) and a 0.1" jumper (such as 969102-0000-DA).

2, MMG3H21NT1     , IC2 IC4 - TRANS HBT 20.5DBM 19.3DB SOT-89
1, SC4503TSKTRT   , IC3 - IC REG BOOST ADJ 1.4A TSOT23-5
1, CONSMA003.062  , P3 - CONN 50 OHM SMA FEMALE EDGE MOUNT FOR 0.062in PCB
1, 961102-6404-AR , JP1 - CONN HEADER VERT SGL 2POS GOLD
1, 969102-0000-DA , SHUNT JUMPER 0.1in BLACK GOLD

https://raw.githubusercontent.com/ha7ilm/opendous/master/Pictures/Upconverter_NoiseSource_Populating.jpg

These parts were omitted to reduce costs since a Noise Source isn't used in an Upconverter. If you use a different amplifier than the MMG3H21NT1 you may need to adjust the value of R12 which is 1R0 (1.0 Ohm). Refer to your amplifier's datasheet. The amplifier supply voltage is 5V from the USB connector.

R11 can be replaced with an EVM-AASA00B14 potentiometer to allow adjustment of the Zener diode current but this has little effect on noise level.

Usage

When using the Noise Source, place the Upconverter into Passthrough Mode (switch away from SMA connector) and install the Noise_Source_EN power jumper prior to powering the Upconverter board through the USB connector. Otherwise the contact bounce will create problems.

For proper operation the Noise Source would need to be characterized using a calibrated Spectrum Analyzer to determine its ENR (Excess Noise Ratio) over its bandwidth. This is an expensive prospect. However, relative measurements between two devices are possible using the Y-Method. More on Y-Method Accuracy.

Let the Noise Source warm up for several minutes then connect it to a receiver and measure average spectrum power density. Repeat for a second receiver. The difference is the relative noise of the two receivers.